suit up like your favorite nfl players, and become a volunteer reader, tutor or mentor with united y. >>> there was a time that tattoos were tabu. something that motorcycle gangs or bad girls got. >> uh-huh. not anymore, though. even the clean cut young pop stars sport these things these days. so tattoo artists are more in demand than ever. where do they learn their trade? abc's alex perez finds out. >> reporter: over the last decades, tattoos have poked through and emerged from a following to being publicly accepted. approximately 36% of americans between 18 to 25 have been inked. 1 in 5 americans have at least one tattoo. tattoos today are so popular, the art is main stream, making some of the artists cult sisters. even the guy who teaches the art got his own 15 minutes of fame. >> this is how you learn. >> tlc's show "tattoo school." and star dr. bill, a 43-year tattoo vet rap, who started his own school called the world's only tattoo school, located in shreveport, louisiana. is it the only tattoo school? >> when we started it was the only one in the world. >> reporter: today, the